Quantitative and cost limits implied on goods depend from whether the goods are sent to Estonia from another EU Member State or non-EU state (or from a third country).
The Member States of the European Union are the following: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, the Netherlands, the United Kingdom.
The ‘special territories’ or the parts of the territory of the Community not covered by Council Directive 2006/112/EC are the following: Åland, the Canary Islands, the Channel Islands, French overseas territories (Guadeloupe, Guiana, Martinique and Reunion), Mount Athos.
In the case of sending goods from the special territories into Estonia the same quantitative and cost limits shall apply as sending goods from a third country. Therefore, goods sent from these territories into Estonia shall be declared at customs and depending from the goods, the value added tax and excise duty shall be paid.
The European Council, by its Decision (EU) 2019/584, extended the United Kingdom's (UK) withdrawal date until 31 October 2019. The Withdrawal Agreement may enter into force on an earlier date, should the Parties complete their respective ratification procedures before 31 October 2019. Consequently, the withdrawal should take place on the first day of the month following the completion of the ratification procedures or on 1 November 2019, whichever is the earliest.
Until the new withdrawal date, the UK will remain a Member State with full rights and obligations.
You can find more information on the webpage "Brexit and its effects on customs clearance and on the trade with the United Kingdom".