Wife's home business has been doing well.

 

She wants to legalize it.

 

She also wants to use the income as base for a mortgage on a property.  The down payment would need to be 50% as she is married to a foreigner. But this isn't about that.

 

It's about the steps for her to legalize her home business.

 

Can she  just register it at her local amphur office? 

 

Then get a tax number, bank account etc. in the business name? She can then transfer this money to her private account and use it as for any mortgage application.

 

Thanks. 

it doesn't matter if she's married to a foreigner, if your names not on the mortgage the deposit can be much less. 

Just register at the ampur. Bank account can stay in her name. GF did this and displayed the business registration and bank statement for numerous bank loans successfully.

So another for the OP would be - How far or if do the bank statements need to go back to prove the business is holding up compared to running costs & out goings ( I would say maybe 6 mths )

It may not be that simple. If your wife conducts business within a legal entity (as you said a business name) and withdraw funds from that legal entity the income becomes taxable twice as income for the business legal entity as well as in her hands. If your wife register a legal entity this entity should amply for the loan and repay it from business income. As csabo said keep it easy, register the business in her name and keep the account in her name. But be aware if you are married you will be responsible for repayment of this loan if her business fail. According to the law you are 50% liable but in practice recon on 100%.