Changing accounting firms in Thailand: what to do and which documents to get back
Can you change accounting firms mid-year? When to start, which documents to request, how to check backlog and access, and the 30-day notification.
You can change accounting firms mid-year, but do it in stages: check your current contract, get documents back, review backlog, hand over system access and change the accountant of record. Avoid doing it close to a major filing deadline, because work can stall while documents are in transit.
When should you start?
Start as soon as you decide, but set the handover after the nearest filing cycle. If only a few days remain before a PP 30 or withholding tax deadline, agree first whether the old or new firm is responsible for that cycle.
Do not wait until the contract ends to ask for documents, and do not switch without knowing which months have been filed.
What should you check with your current firm?
- The contract end date and termination terms
- Work paid for but not yet delivered
- Returns filed and evidence of filing
- Work in progress
- Tax or balances still to be paid
Terminate politely and in writing, then ask for a clear list of what will be handed over so everyone sees the same thing.
Which documents should you get back?
- Account books and related reports
- The latest trial balance and prior-year financial statements
- Copies of filed returns, such as PP 30, PND 1, PND 3, PND 53, PND 50 and PND 51
- Tax invoices, receipts and supporting documents
- Lists of assets, receivables, payables and inventory
- Payroll and social security data
Accounting documents must be kept for at least 5 years from the closing date, and your business keeps that duty even if the provider changes. See the wider picture in the monthly accounting documents checklist.
Which system access must be handled?
List the relevant accounts, such as tax filing, DBD e-Filing and social security systems.
- Have the business owner hold the main credentials
- Change passwords, and any recovery phone or email that is not the business's own
- Grant access only to those who need it
- Save past filing evidence before removing old access
Do not send passwords through group chats or files that many people can open.
How do you change the accountant of record?
The Department of Business Development has accountants notify details through the e-Accountant system. Adding or cancelling a business they handle must be done within 30 days of the change.
As a business, agree with the old and new accountants who will notify and when, then ask for evidence, so there is no period when responsibility is unclear.
How do you review backlog before restarting?
- Compare bank balances with the books
- Check input and output tax against filed returns
- See which months have not been filed
- Check receivables, payables and inventory balances
- Record any errors found and their effect
If you find a problem, determine whether it came from documents or recording, then correct it from the evidence. Do not rush to assign blame without data, and do not adjust balances just to make them match.
What should you ask a new firm before changing?
- Which month will they take over from?
- How is backlog work charged?
- Who will be the accountant of record?
- How are documents sent, and who gives deadline reminders?
If you are comparing options, see what drives accounting fees. If you want help with a takeover, our team can discuss the overall picture before starting.
Frequently asked questions
What if your old firm will not return documents?
Ask in writing, listing the items and a deadline, and check your contract. If you still do not receive them, seek legal advice or contact the relevant agency, and begin requesting what you can from your bank or trading partners.
Do the whole year's accounts need redoing?
Not always. If the existing data can be verified, a new firm can continue from the balances brought forward. If documents are missing or balances do not match, some correction or backlog work may be needed.
Can you change close to year end?
Yes, but be careful. Check the deadlines for closing your books and DBD submission before setting a handover date.
Sources
Checked on November 3, 2026
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