What records do plumbers need for self-assessment?

What records do plumbers need for self-assessment?

Self-assessment can feel like a chore, especially when you’d rather be on the tools than sorting receipts. But if you’re a plumber working for yourself in the UK—whether you’re a sole trader, a contractor taking on regular subbie work, or you run a small plumbing business—good records are what turn tax time from stressful guesswork into a straightforward routine. The better your paperwork, the easier it is to prove what you earned, what you spent, what you’re allowed to claim, and what you actually owe.

This guide explains, in practical terms, the records plumbers typically need for self-assessment, how long to keep them, and how to organise them so you can answer questions quickly. And because record-keeping is only useful when it’s simple enough to stick with, we’ll also show how a free invoicing tool like invoice24 can make it easier to track income, keep customer details tidy, and maintain a clean trail from quote to invoice to payment—without paying for complicated software.

Why good records matter for plumbers

Record-keeping isn’t just about “doing your tax.” For plumbers, it affects everything from cash flow to credibility. Clear records help you:

1) Complete your self-assessment accurately. Your tax return is only as good as the numbers you use. Missing invoices or overlooked costs can mean overpaying, underpaying, or needing corrections later.

2) Know your real profit. Many tradespeople judge success by money in the bank. But your bank balance doesn’t tell you which jobs were profitable once materials, fuel, tool replacement, and time are accounted for.

3) Handle questions confidently. If you ever need to explain figures—whether to HMRC, a mortgage adviser, an accountant, or a lender—good records save time and stress.

4) Get paid faster. Professional invoices with clear payment terms reduce delays and misunderstandings. When you can quickly resend an invoice or show what was agreed, you’re in control.

5) Grow with less chaos. If you take on an apprentice, start using subcontractors, or move into bigger projects, your record system has to keep up.

Even if your business is small, the right habit now prevents a mountain of admin later.

The core record categories plumbers should keep

Think of self-assessment records as falling into two big buckets: money coming in and money going out. Around those sit supporting records that explain the “why” behind transactions—job details, customer agreements, mileage logs, and documents related to equipment and assets.

Here are the core categories plumbers should keep in a practical, real-world way.

1) Income records: what you earned

Your income records should show who paid you, what for, when, and how much. For many plumbers, income comes from a mix of domestic call-outs, quoted jobs, maintenance plans, landlord work, insurance-related repairs, and sometimes subcontracting to larger firms.

Invoices issued are the backbone of income records. Each invoice should include:

- Your business name (and trading name if relevant)

- Customer name and address (or at least a clear identifier)

- Invoice number (unique and sequential is ideal)

- Invoice date

- Description of work (clear enough to identify the job)

- Labour and materials breakdown (recommended)

- Total amount charged

- Payment terms (due date, accepted payment methods)

If you’re using invoice24, keeping these details consistent is much easier. A free invoicing app helps you generate professional invoices quickly, and the invoices themselves become part of your organised record set. Instead of hunting through messages to work out what you charged Mrs Smith for the boiler service, you can pull up the invoice and see it instantly.

Cash payments and receipts should also be recorded. If a customer hands you cash, you still need a record of the income. That can be an invoice marked as paid, a receipt you issue, or a clear entry in your records that ties the cash to a job.

Bank statements are another key income record. Even if you keep excellent invoices, bank statements help confirm when you were paid and can fill gaps if a customer paid by transfer without a clear reference.

Online payment records (if you use payment links, card readers, or e-wallets) should be saved. Payment platforms often charge fees, and those fees may be business expenses—so you want both the gross payment record and the fee breakdown.

Job sheets or work logs can be helpful support. They’re not always required to submit your return, but they’re useful if you need to explain why there was a particular charge, or to match a payment to a specific job.

Tip for plumbers: Make sure your invoice descriptions are specific enough to jog your memory later. “Plumbing work” is vague; “Replace kitchen tap and isolation valves; supply and fit customer-approved tap” is much better.

2) Expense records: what you spent

To work out taxable profit, you subtract allowable business expenses from business income. The easiest way to handle this is to keep evidence (receipts/invoices) and a clear method of categorising costs. Plumbers tend to have a lot of small purchases: fittings, consumables, parking, adhesives, and emergency parts runs. Those add up, and if you don’t track them, you can accidentally overstate your profit and overpay tax.

Here are common expense categories for plumbers and the types of records to keep.

Materials and parts

This includes pipe, valves, fixings, fittings, radiators, taps, traps, seals, washers, solder, flux, adhesives, sealants, and any parts you buy specifically for jobs. Keep:

- Supplier receipts and invoices

- Delivery notes (useful if invoices are vague)

- Trade account statements

It’s worth noting that customers sometimes reimburse materials separately. If you buy parts and recharge them, it’s still cleaner to record the purchase as an expense and the recharge as income, rather than netting them off in your head. Proper invoicing helps you show the trail: bought materials, used on job, charged customer.

Tooling and equipment

Plumbing tools range from small hand tools to expensive kit like press tools, pipe freezers, inspection cameras, and power tools. Keep:

- Purchase receipts/invoices

- Warranty documents

- Finance or hire purchase agreements if applicable

- Repair/servicing invoices

Some tools may be treated differently for tax depending on whether they’re considered equipment with a longer life. In practical record terms, you still keep the receipts and note what the item is and when you bought it.

Vehicle costs and travel

For many plumbers, the van is the business. You’ll typically want records for:

- Fuel receipts

- Insurance documents

- MOT certificates

- Servicing and repair invoices

- Tyres

- Breakdown cover

- Parking, tolls, congestion charges (where applicable)

There are different ways tradespeople track vehicle costs, but whichever method you use, you need supporting records and consistency. Even if you don’t keep every fuel receipt, having a sensible system is important. Many plumbers find it easiest to keep a folder (digital or physical) specifically for vehicle expenses.

Mobile phone and internet

Most plumbers use their phone for calls, WhatsApp messages, photos, maps, and scheduling. Keep:

- Monthly bills

- Pay-as-you-go top-up receipts

- Device purchase receipts if used for business

If the phone is used for both personal and business, keep the bills and make a reasonable note of the business proportion you’re claiming.

Workwear and protective equipment

Workwear is a common area of confusion. In practical terms, keep receipts for:

- Protective boots

- Gloves, eye protection, masks

- Branded uniform or protective clothing

- Specialist clothing required for the job

Plain everyday clothing is not the same as protective equipment. Your records should make it obvious what the purchase was for.

Training and certifications

If you pay for relevant training, courses, or professional certifications, keep:

- Course invoices/receipts

- Proof of attendance/completion

- Membership fees if required for certification

Plumbers often have renewals and safety-related training. Keeping all certification documents in one place is useful for customers as well as tax time.

Advertising and marketing

Even if your business comes mostly from word-of-mouth, you might pay for:

- Website hosting

- Business cards and flyers

- Local directory listings

- Branded van signage

- Online ads

Keep receipts, contracts, and invoices. Marketing costs can be easy to forget because they might be a once-a-year payment.

Insurance

Plumbers commonly hold public liability insurance and may have tools insurance or professional indemnity depending on the work. Keep:

- Policy documents

- Payment confirmations

These documents often help with customer confidence too, so storing them neatly pays off in more than one way.

Office and admin costs

This covers costs like:

- Stationery

- Printer ink

- Accounting fees

- Software subscriptions

If you use a free invoicing app like invoice24, you can reduce this category significantly because you’re not paying for heavy software just to generate invoices. Lower overheads mean more of your money stays in your pocket.

Bank and payment processing fees

Keep records of:

- Bank account charges for business accounts

- Card reader fees

- Payment platform charges

These small fees add up over a year, especially if you take lots of card payments.

Subcontractors and labour

If you pay another plumber or labourer to help you, keep:

- Their invoices

- Proof of payment

- Any written agreements or job-specific paperwork

Even if it’s a mate helping you on a big job, you want a clear record of what you paid and why.

3) Records for quotes, estimates, and job agreements

Not everything is an invoice. Plumbers often give quotes first, then convert to invoices once work is done. Keeping a record of quotes and agreements helps you stay consistent and protects you if there’s ever a dispute about what was included.

Useful records include:

- Written quotes or estimates

- Emails or messages confirming price and scope

- Photos of the job before and after

- Notes about customer-supplied parts

- Change requests and variations (e.g., “customer asked to move radiator location”)

Good admin is a form of risk management. If you’ve ever had a customer say “I thought that was included,” you’ll appreciate the value of having job details stored properly.

invoice24 can support this workflow by making it easy to create invoices that reflect what was agreed and what was delivered. Even if you still quote in your own way, turning that final agreed scope into a clean invoice reduces confusion and keeps your records consistent.

4) Mileage and travel logs

If you track business travel, you’ll want a system that shows when and why you travelled. For plumbers, this might include:

- Call-outs

- Site visits for quoting

- Supplier runs (especially if job-related)

- Travel between jobs

A mileage log typically includes:

- Date

- Start location and end location

- Purpose of trip (job/customer reference)

- Miles travelled

You don’t need to overcomplicate it. The key is consistency and clarity. A simple spreadsheet, a notebook kept in the van, or a mileage app can work—just make sure you can tie trips back to business activity.

5) Records for the use of home as an office

Many self-employed plumbers handle admin at home: scheduling, calls, storing tools, sorting paperwork. If you claim a portion of home costs, keep records of:

- Utility bills (electric, gas, water)

- Internet bills

- Council tax statements

- Mortgage interest statements or rent agreements (as relevant)

The important point is to keep the original bills and have a consistent method for how you calculate the business share. Even if you claim a simplified amount, keeping basic household bills is still a sensible backup.

6) Business bank account records

While not mandatory for everyone, having a separate business bank account makes record-keeping dramatically easier. It creates a cleaner separation between personal spending and business spending. Whether you do this or not, you should keep:

- Bank statements

- Payment confirmations

- Loan statements if you borrowed for the business

If you mix personal and business in one account, your records should clearly explain which transactions are business-related. That can be time-consuming. A separate account saves admin hours, and time is money.

7) VAT records (if applicable)

Not every plumber is VAT registered. But if you are, you need extra records to support VAT reporting. These typically include:

- VAT invoices issued

- VAT receipts for purchases (where VAT was charged)

- VAT return calculations

- Evidence of VAT rates applied

If you’re not VAT registered, you still keep invoices and receipts, but you’re not tracking VAT in the same way. If you ever do register, your record system should be ready to scale.

Even for non-VAT plumbers, using invoice24 to issue clear invoices helps maintain professionalism and makes it easier to switch processes later if your business grows.

8) CIS records (if you do subcontracting)

Some plumbers do work as subcontractors in construction settings where the Construction Industry Scheme (CIS) may apply. If you receive deductions, you need to keep:

- Payment and deduction statements provided by contractors

- Invoices you issued to contractors

- Proof of payments received

These documents matter because they affect how your tax is calculated. If you do both domestic and CIS work, it’s especially important to keep a clear separation of records. A consistent invoicing process helps you identify which jobs were for which payer and which category of work.

9) Asset records: big purchases and long-term kit

Some purchases aren’t just “expenses”; they’re assets you’ll use over several years—like a van, a high-end power tool set, or specialist equipment. Keep records that show:

- Purchase price and date

- Supplier details

- Any finance terms

- Sale or disposal records if you sell the asset later

Practical tip: create a simple list called “Major equipment and assets” and add to it whenever you buy something significant. Attach the receipt or invoice to that entry so you can find it easily later.

10) Records for bad debts and refunds

Most plumbers eventually deal with a non-payer or someone who disputes a charge. To keep your records clean, track:

- Unpaid invoices

- Payment chaser messages (optional but useful)

- Any formal dispute notes

- Refunds issued and why

- Partial payments

This is another reason invoicing matters. When every job is tied to an invoice number, it’s easier to see what’s outstanding and what’s resolved. With invoice24, you can keep your customer invoices organised so you’re not relying on memory when you’re juggling multiple jobs.

How long should plumbers keep records?

As a rule of thumb, keep your records long enough that you can support the figures you’ve submitted. Many plumbers keep records for several years after the relevant tax year ends. In practice, storing digital records is usually simple and cheap, so it’s sensible to keep a well-organised archive even beyond the minimum you think you’ll need.

Good record-keeping is not just about retention—it’s about retrieval. If you can’t find the receipt, it might as well not exist. This is why a simple system you actually use beats a perfect system you abandon.

Paper vs digital: what’s best for plumbers?

Plumbers are rarely sitting at a desk all day. You might buy parts at a merchant, get a receipt, shove it in the glovebox, then discover it months later. Paper-based record-keeping works until it doesn’t.

Paper records can be fine if you:

- Store them weekly (not “sometime later”)

- Use envelopes or folders by month

- Keep invoices in a separate section

Digital records are usually easier because you can:

- Store photos/scans of receipts

- Search by keyword or date

- Back up automatically

- Reduce lost paperwork

For most plumbers, a hybrid approach works: keep important originals where necessary, but capture digital copies so you can actually find things when needed.

invoice24 fits naturally into a digital approach because it gives you a clean, searchable record of invoices you’ve issued. That means less paper, fewer missing documents, and a more professional customer experience.

A practical record-keeping system plumbers can stick to

Here’s a simple routine that works well for trades:

Daily (2 minutes): Send invoices promptly when the job is complete. If you invoice the same day, you’re less likely to forget details or undercharge. Using invoice24 makes this fast—especially when you can reuse customer details and keep invoice numbering consistent.

Weekly (10–20 minutes): Gather receipts and log expenses. If you’re not using an accountant yet, a simple spreadsheet with columns for date, supplier, category, amount, and notes is enough. The important part is doing it weekly, not yearly.

Monthly (30 minutes): Reconcile your bank statements. Check that all invoices marked paid match the payments received, and note any late payers. This also helps you spot unusual spending or subscriptions you no longer need.

Quarterly (optional but smart): Do a quick profit check: total income minus total expenses. This helps you plan for tax and avoid nasty surprises.

Yearly (tax prep): Put everything together for self-assessment: total income, total allowable expenses, and notes on any unusual items.

This kind of routine is easier when invoicing is not a headache. invoice24 is designed to keep invoicing simple, which helps the rest of your record system fall into place.

What details should be on a plumber’s invoice for clean tax records?

A good invoice isn’t only for the customer—it’s also for you later. When you’re preparing your self-assessment, you don’t want to look at an invoice and wonder what the job was. For cleaner records, include:

- A meaningful job description

- Labour and materials separated (even if you charge a fixed price)

- Date work was carried out (if different from invoice date)

- Customer address (helpful if you need to confirm travel or job details)

- Any discounts clearly shown

- Payment method and due date

If you use invoice24, you can build a consistent invoice template and keep everything uniform. That consistency matters more than people think; it reduces mistakes and speeds up admin.

Common record-keeping mistakes plumbers make

Plumbers are busy. These mistakes are common and avoidable:

Not invoicing promptly. The longer you wait, the more likely you forget small extras, undercharge, or confuse job details between customers.

Losing small receipts. A handful of missing £10–£30 receipts each month becomes a large chunk of unclaimed expenses over a year.

Mixing personal and business spending. This creates messy bank statements and makes it harder to prove what relates to the business.

Not tracking unpaid invoices. If you don’t know what you’re owed, you’re effectively giving customers an interest-free loan.

Relying on memory. Memory is not an accounting system. A simple written trail beats “I think it was about…” every time.

Overcomplicating everything. Some plumbers try to build a perfect system and then give up. A simple system that you keep using is the best system.

A free invoice tool like invoice24 helps reduce several of these issues at once by making invoicing fast, organised, and easy to review later.

How invoice24 helps plumbers stay ready for self-assessment

Even if you’re not trying to become an admin expert, the right tools can make record-keeping nearly effortless. invoice24 is built to support everyday invoicing without locking you into expensive plans, confusing dashboards, or features you don’t need. For plumbers, it helps in practical ways that matter:

Professional invoices in minutes. When invoicing is easy, you’re more likely to do it immediately after the job—when details are fresh and your cash flow benefits most.

Clear income trail. Each invoice becomes a record of income with a date, a customer, and a job description. That’s exactly what you need when you’re pulling together totals for self-assessment.

Consistent invoice numbering. A tidy invoice sequence makes your records easier to audit and easier for you to search through later.

Customer details saved. If you do repeat work for landlords, letting agents, or regular customers, you’ll appreciate not having to retype details each time. Consistency reduces mistakes and speeds up billing.

Less time chasing paperwork. When your invoices are stored in one place, you’re not digging through old messages or notebooks to find what you charged.

Supports a simple workflow. invoice24 isn’t trying to be everything. That’s a good thing. Plumbers want a tool that does the job: get invoices out, look professional, and keep records straightforward.

Competitor tools may offer a huge list of features, but many self-employed plumbers don’t need complexity—they need reliability, clarity, and speed. invoice24 prioritises the essentials so you can spend more time earning and less time doing admin.

How to organise your records alongside invoice24

invoice24 can handle your invoicing records, and then you can build a simple structure around it for expenses and supporting documents. Here’s a practical setup:

Create folders by tax year:

- 2025–2026

- 2026–2027

Inside each year, create folders like:

- Income (invoices, payment confirmations)

- Materials and parts

- Vehicle

- Tools and equipment

- Phone and internet

- Insurance

- Training

- Marketing

- Subcontractors

Weekly habit: take photos of receipts and drop them into the right folder. Name them simply, for example:

- 2026-02-14_Screwfix_PipeFittings_32.80

- 2026-03-01_TescoFuel_68.12

When invoicing is already handled neatly inside invoice24, this folder structure becomes much easier to maintain because you’re not trying to organise everything at once.

What if you use an accountant?

An accountant can be valuable, especially if your work includes subcontracting, VAT, or you’re growing quickly. But even with an accountant, you still need to keep records. The difference is that your goal becomes “making it easy for the accountant to do their job,” which usually means:

- Clean income records (invoices and bank statements)

- Categorised expenses with receipts

- Notes on anything unusual

Using invoice24 helps here because you can produce a clear set of invoices and totals without messy spreadsheets or handwritten notes. Your accountant will thank you, and you’ll likely spend less time (and possibly less money) on back-and-forth.

Preparing for self-assessment: a plumber’s checklist

When it’s time to prepare your self-assessment, you’ll want the following ready:

Income:

- A list of invoices issued (invoice24 makes this much easier)

- Bank statements showing payments received