•The deadline is the income tax filing deadline for the year in which the event occurred (Income Tax Act art. 229). If it falls on a weekend or public holiday, it moves to the next day
•File with the head of the tax office for your place of tax payment. Even if your office sits in a different district, no filing with any other tax office is needed
•From October 1, 2026 the general counter at every tax office accepts filings from 9:00 to 15:00 as a rule. Outside that window you can still complete procedures if you arrive within office hours (8:30 to 17:00). Tax offices do not operate on Saturdays, Sundays, public holidays or from December 29 to January 3, but you can file by post or through the after-hours drop box
•The blue-return application is due by March 15 of the year you want it to apply to — or within two months of starting the business if you started it on or after January 16 of that year
•Registering as a qualified invoice issuer is optional. A tax-exempt business that registers must file consumption tax returns for two years from the registration date, and that holds even if the registration is later withdrawn (you remain a taxable business through the tax period containing the second anniversary)
•A tax-exempt business can name a desired registration date, which must be at least 15 days after the application is submitted. If you have just started a business, applying by the last day of the tax period backdates the registration to the first day of that period — for a sole proprietor that is January 1 of the year you started, not the day you started
•Once registered, your details are published on the NTA's public register of qualified invoice issuers